1. Field of the Invention
This invention relates to gaseous state fluid regulation systems and more particularly to a feed system for a bi-propellant, pressure-fed, rocket engine which utilizes a mass flow rate regulator which contains a bellows which is responsive to pressure and temperature changes to activate a poppet which controls the area of a propellant fluid flow passageway.
2. Description of the Prior Art
Pressure regulators that simply control pressure are normally suitable for flow control where there are small temperature fluctuations. Under these conditions, such pressure regulators establish satisfactory and predictable flows. However, these pressure regulators, in only controlling pressure do not compensate for changes in density that occur with temperature changes. In systems, such as the feed system for a fluid fueled rocket engine combustor, where large temperature variations occur, the flow regulators require commensurate monitoring of fluid density changes in order to maintain the desired mass flow rate.
The typical scenario for the feed system of a bi-propellant pressure fed fluid fueled rocket engine combustor is as follows:
The rocket propellants, hydrogen (H.sub.2) and oxygen (O.sub.2), are stored (and supplied) in tanks that are initially at high pressure and low temperature (2000 psi and 200.degree. R). The pressure and temperature change as the contents of the tanks are consumed and heated during operation (to 300 psi and 600.degree. R). The propellant supply can easily be controlled to a constant feed pressure of 300 psi, but the temperature change of the regulated gas could change the density by a factor of three. Some method is required to compensate for the density change due to temperature.
Two conventional methods for compensating for density changes, a servo regulator system and a multiple valve array system, were evaluated by Rockwell International Corporation for use in the Space Station program. The servo regulator system is designated generally as 100 in FIG. 3. Hydrogen and oxygen propellants, initially stored in tanks 110 which are heated by means 111, flow through conventional pressure regulators 112 which control the feed pressure at approximately 300 psi. The flow of propellants are then regulated by complex servo valves 114 which control the combustor inlet pressure as a function of temperature. As illustrated in the Figure, the servo regulator system 100 requires pressure and temperature transducers 116, 118, power sources 120, and a remotely located electronic servo controller. Each fluid propellant flows through an on/off thruster valve 122 prior to its introduction into the combustor 124.
The multiple valve array system (not illustrated) also requires pressure and temperature transducers, power sources, and an electronic controller. In addition, there are several valves, each having a control orifice. Flow may be controlled by using only one orifice or any combination of orifices.
Both the servo and multiple valve array concepts were found to provide proper control to the rocket combustor, but they would require active control from the central space station computer. The space station complex has many combustors that are located at the extremities to provide the force moments necessary to keep the exhaust away from instruments. All the electronic components, such as the servo valve, multiple valves, and transducers must be connected to computers and require cabling for utilization. Therefore, weight limitations as well as the complexity involved in attempting to utilize several servo valve controls makes a stand-alone, mechanical regulator appealing.
In FIG. 1 of U.S. Pat. No. 4,522,219 issued to I. Ohkata a conventional exhaust valve is shown for exhausting condensed water of steam for a Diesel locomotive which travels in a cold environment. In this valve, fluid flows freely from a steam feed pipe into a valve body. The valve body contains a bellows connected to a rod. The lower end of the rod contains a valve element which opens an exhaust port when the bellows is contracted and closes the exhaust port when the bellows is expanded. When the steam from the feed pipe is partly cooled to produce condensed water, the water flows into the valve body. The relatively cool water cools and contracts the bellows. The valve element therefore moves up opening the exhaust port and allowing the discharge of condensed water.